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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.2"></a>
<span class="sourceLineNo">003</span> * you may not use this file except in compliance with the License.<a name="line.3"></a>
<span class="sourceLineNo">004</span> * You may obtain a copy of the License at<a name="line.4"></a>
<span class="sourceLineNo">005</span> *<a name="line.5"></a>
<span class="sourceLineNo">006</span> *     http://www.apache.org/licenses/LICENSE-2.0<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * Unless required by applicable law or agreed to in writing, software<a name="line.8"></a>
<span class="sourceLineNo">009</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.9"></a>
<span class="sourceLineNo">010</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.10"></a>
<span class="sourceLineNo">011</span> * See the License for the specific language governing permissions and<a name="line.11"></a>
<span class="sourceLineNo">012</span> * limitations under the License.<a name="line.12"></a>
<span class="sourceLineNo">013</span> */<a name="line.13"></a>
<span class="sourceLineNo">014</span>package org.apache.commons.io.input;<a name="line.14"></a>
<span class="sourceLineNo">015</span><a name="line.15"></a>
<span class="sourceLineNo">016</span>import static org.apache.commons.io.IOUtils.EOF;<a name="line.16"></a>
<span class="sourceLineNo">017</span><a name="line.17"></a>
<span class="sourceLineNo">018</span>// import javax.annotation.concurrent.GuardedBy;<a name="line.18"></a>
<span class="sourceLineNo">019</span>import java.io.EOFException;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.io.IOException;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.io.InputStream;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.io.InterruptedIOException;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.nio.ByteBuffer;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.util.Objects;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.concurrent.ExecutorService;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.concurrent.Executors;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.util.concurrent.TimeUnit;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.util.concurrent.atomic.AtomicBoolean;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.concurrent.locks.Condition;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.util.concurrent.locks.ReentrantLock;<a name="line.30"></a>
<span class="sourceLineNo">031</span><a name="line.31"></a>
<span class="sourceLineNo">032</span>/**<a name="line.32"></a>
<span class="sourceLineNo">033</span> * Implements {@link InputStream} to asynchronously read ahead from an underlying input stream when a specified amount<a name="line.33"></a>
<span class="sourceLineNo">034</span> * of data has been read from the current buffer. It does so by maintaining two buffers: an active buffer and a read<a name="line.34"></a>
<span class="sourceLineNo">035</span> * ahead buffer. The active buffer contains data which should be returned when a read() call is issued. The read ahead<a name="line.35"></a>
<span class="sourceLineNo">036</span> * buffer is used to asynchronously read from the underlying input stream. When the current active buffer is exhausted,<a name="line.36"></a>
<span class="sourceLineNo">037</span> * we flip the two buffers so that we can start reading from the read ahead buffer without being blocked by disk I/O.<a name="line.37"></a>
<span class="sourceLineNo">038</span> * &lt;p&gt;<a name="line.38"></a>
<span class="sourceLineNo">039</span> * This class was ported and adapted from Apache Spark commit 933dc6cb7b3de1d8ccaf73d124d6eb95b947ed19.<a name="line.39"></a>
<span class="sourceLineNo">040</span> * &lt;/p&gt;<a name="line.40"></a>
<span class="sourceLineNo">041</span> *<a name="line.41"></a>
<span class="sourceLineNo">042</span> * @since 2.9.0<a name="line.42"></a>
<span class="sourceLineNo">043</span> */<a name="line.43"></a>
<span class="sourceLineNo">044</span>public class ReadAheadInputStream extends InputStream {<a name="line.44"></a>
<span class="sourceLineNo">045</span><a name="line.45"></a>
<span class="sourceLineNo">046</span>    private static final ThreadLocal&lt;byte[]&gt; oneByte = ThreadLocal.withInitial(() -&gt; new byte[1]);<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span>    /**<a name="line.48"></a>
<span class="sourceLineNo">049</span>     * Creates a new daemon executor service.<a name="line.49"></a>
<span class="sourceLineNo">050</span>     *<a name="line.50"></a>
<span class="sourceLineNo">051</span>     * @return a new daemon executor service.<a name="line.51"></a>
<span class="sourceLineNo">052</span>     */<a name="line.52"></a>
<span class="sourceLineNo">053</span>    private static ExecutorService newExecutorService() {<a name="line.53"></a>
<span class="sourceLineNo">054</span>        return Executors.newSingleThreadExecutor(ReadAheadInputStream::newThread);<a name="line.54"></a>
<span class="sourceLineNo">055</span>    }<a name="line.55"></a>
<span class="sourceLineNo">056</span><a name="line.56"></a>
<span class="sourceLineNo">057</span>    /**<a name="line.57"></a>
<span class="sourceLineNo">058</span>     * Creates a new daemon thread.<a name="line.58"></a>
<span class="sourceLineNo">059</span>     *<a name="line.59"></a>
<span class="sourceLineNo">060</span>     * @param r the thread's runnable.<a name="line.60"></a>
<span class="sourceLineNo">061</span>     * @return a new daemon thread.<a name="line.61"></a>
<span class="sourceLineNo">062</span>     */<a name="line.62"></a>
<span class="sourceLineNo">063</span>    private static Thread newThread(final Runnable r) {<a name="line.63"></a>
<span class="sourceLineNo">064</span>        final Thread thread = new Thread(r, "commons-io-read-ahead");<a name="line.64"></a>
<span class="sourceLineNo">065</span>        thread.setDaemon(true);<a name="line.65"></a>
<span class="sourceLineNo">066</span>        return thread;<a name="line.66"></a>
<span class="sourceLineNo">067</span>    }<a name="line.67"></a>
<span class="sourceLineNo">068</span><a name="line.68"></a>
<span class="sourceLineNo">069</span>    private final ReentrantLock stateChangeLock = new ReentrantLock();<a name="line.69"></a>
<span class="sourceLineNo">070</span><a name="line.70"></a>
<span class="sourceLineNo">071</span>    // @GuardedBy("stateChangeLock")<a name="line.71"></a>
<span class="sourceLineNo">072</span>    private ByteBuffer activeBuffer;<a name="line.72"></a>
<span class="sourceLineNo">073</span><a name="line.73"></a>
<span class="sourceLineNo">074</span>    // @GuardedBy("stateChangeLock")<a name="line.74"></a>
<span class="sourceLineNo">075</span>    private ByteBuffer readAheadBuffer;<a name="line.75"></a>
<span class="sourceLineNo">076</span><a name="line.76"></a>
<span class="sourceLineNo">077</span>    // @GuardedBy("stateChangeLock")<a name="line.77"></a>
<span class="sourceLineNo">078</span>    private boolean endOfStream;<a name="line.78"></a>
<span class="sourceLineNo">079</span><a name="line.79"></a>
<span class="sourceLineNo">080</span>    // @GuardedBy("stateChangeLock")<a name="line.80"></a>
<span class="sourceLineNo">081</span>    // true if async read is in progress<a name="line.81"></a>
<span class="sourceLineNo">082</span>    private boolean readInProgress;<a name="line.82"></a>
<span class="sourceLineNo">083</span><a name="line.83"></a>
<span class="sourceLineNo">084</span>    // @GuardedBy("stateChangeLock")<a name="line.84"></a>
<span class="sourceLineNo">085</span>    // true if read is aborted due to an exception in reading from underlying input stream.<a name="line.85"></a>
<span class="sourceLineNo">086</span>    private boolean readAborted;<a name="line.86"></a>
<span class="sourceLineNo">087</span><a name="line.87"></a>
<span class="sourceLineNo">088</span>    // @GuardedBy("stateChangeLock")<a name="line.88"></a>
<span class="sourceLineNo">089</span>    private Throwable readException;<a name="line.89"></a>
<span class="sourceLineNo">090</span><a name="line.90"></a>
<span class="sourceLineNo">091</span>    // @GuardedBy("stateChangeLock")<a name="line.91"></a>
<span class="sourceLineNo">092</span>    // whether the close method is called.<a name="line.92"></a>
<span class="sourceLineNo">093</span>    private boolean isClosed;<a name="line.93"></a>
<span class="sourceLineNo">094</span><a name="line.94"></a>
<span class="sourceLineNo">095</span>    // @GuardedBy("stateChangeLock")<a name="line.95"></a>
<span class="sourceLineNo">096</span>    // true when the close method will close the underlying input stream. This is valid only if<a name="line.96"></a>
<span class="sourceLineNo">097</span>    // `isClosed` is true.<a name="line.97"></a>
<span class="sourceLineNo">098</span>    private boolean isUnderlyingInputStreamBeingClosed;<a name="line.98"></a>
<span class="sourceLineNo">099</span><a name="line.99"></a>
<span class="sourceLineNo">100</span>    // @GuardedBy("stateChangeLock")<a name="line.100"></a>
<span class="sourceLineNo">101</span>    // whether there is a read ahead task running,<a name="line.101"></a>
<span class="sourceLineNo">102</span>    private boolean isReading;<a name="line.102"></a>
<span class="sourceLineNo">103</span><a name="line.103"></a>
<span class="sourceLineNo">104</span>    // Whether there is a reader waiting for data.<a name="line.104"></a>
<span class="sourceLineNo">105</span>    private final AtomicBoolean isWaiting = new AtomicBoolean(false);<a name="line.105"></a>
<span class="sourceLineNo">106</span><a name="line.106"></a>
<span class="sourceLineNo">107</span>    private final InputStream underlyingInputStream;<a name="line.107"></a>
<span class="sourceLineNo">108</span><a name="line.108"></a>
<span class="sourceLineNo">109</span>    private final ExecutorService executorService;<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span>    private final boolean shutdownExecutorService;<a name="line.111"></a>
<span class="sourceLineNo">112</span><a name="line.112"></a>
<span class="sourceLineNo">113</span>    private final Condition asyncReadComplete = stateChangeLock.newCondition();<a name="line.113"></a>
<span class="sourceLineNo">114</span><a name="line.114"></a>
<span class="sourceLineNo">115</span>    /**<a name="line.115"></a>
<span class="sourceLineNo">116</span>     * Creates an instance with the specified buffer size and read-ahead threshold<a name="line.116"></a>
<span class="sourceLineNo">117</span>     *<a name="line.117"></a>
<span class="sourceLineNo">118</span>     * @param inputStream The underlying input stream.<a name="line.118"></a>
<span class="sourceLineNo">119</span>     * @param bufferSizeInBytes The buffer size.<a name="line.119"></a>
<span class="sourceLineNo">120</span>     */<a name="line.120"></a>
<span class="sourceLineNo">121</span>    public ReadAheadInputStream(final InputStream inputStream, final int bufferSizeInBytes) {<a name="line.121"></a>
<span class="sourceLineNo">122</span>        this(inputStream, bufferSizeInBytes, newExecutorService(), true);<a name="line.122"></a>
<span class="sourceLineNo">123</span>    }<a name="line.123"></a>
<span class="sourceLineNo">124</span><a name="line.124"></a>
<span class="sourceLineNo">125</span>    /**<a name="line.125"></a>
<span class="sourceLineNo">126</span>     * Creates an instance with the specified buffer size and read-ahead threshold<a name="line.126"></a>
<span class="sourceLineNo">127</span>     *<a name="line.127"></a>
<span class="sourceLineNo">128</span>     * @param inputStream The underlying input stream.<a name="line.128"></a>
<span class="sourceLineNo">129</span>     * @param bufferSizeInBytes The buffer size.<a name="line.129"></a>
<span class="sourceLineNo">130</span>     * @param executorService An executor service for the read-ahead thread.<a name="line.130"></a>
<span class="sourceLineNo">131</span>     */<a name="line.131"></a>
<span class="sourceLineNo">132</span>    public ReadAheadInputStream(final InputStream inputStream, final int bufferSizeInBytes,<a name="line.132"></a>
<span class="sourceLineNo">133</span>        final ExecutorService executorService) {<a name="line.133"></a>
<span class="sourceLineNo">134</span>        this(inputStream, bufferSizeInBytes, executorService, false);<a name="line.134"></a>
<span class="sourceLineNo">135</span>    }<a name="line.135"></a>
<span class="sourceLineNo">136</span><a name="line.136"></a>
<span class="sourceLineNo">137</span>    /**<a name="line.137"></a>
<span class="sourceLineNo">138</span>     * Creates an instance with the specified buffer size and read-ahead threshold<a name="line.138"></a>
<span class="sourceLineNo">139</span>     *<a name="line.139"></a>
<span class="sourceLineNo">140</span>     * @param inputStream The underlying input stream.<a name="line.140"></a>
<span class="sourceLineNo">141</span>     * @param bufferSizeInBytes The buffer size.<a name="line.141"></a>
<span class="sourceLineNo">142</span>     * @param executorService An executor service for the read-ahead thread.<a name="line.142"></a>
<span class="sourceLineNo">143</span>     * @param shutdownExecutorService Whether or not to shutdown the given ExecutorService on close.<a name="line.143"></a>
<span class="sourceLineNo">144</span>     */<a name="line.144"></a>
<span class="sourceLineNo">145</span>    private ReadAheadInputStream(final InputStream inputStream, final int bufferSizeInBytes,<a name="line.145"></a>
<span class="sourceLineNo">146</span>        final ExecutorService executorService, final boolean shutdownExecutorService) {<a name="line.146"></a>
<span class="sourceLineNo">147</span>        if (bufferSizeInBytes &lt;= 0) {<a name="line.147"></a>
<span class="sourceLineNo">148</span>            throw new IllegalArgumentException(<a name="line.148"></a>
<span class="sourceLineNo">149</span>                "bufferSizeInBytes should be greater than 0, but the value is " + bufferSizeInBytes);<a name="line.149"></a>
<span class="sourceLineNo">150</span>        }<a name="line.150"></a>
<span class="sourceLineNo">151</span>        this.executorService = Objects.requireNonNull(executorService, "executorService");<a name="line.151"></a>
<span class="sourceLineNo">152</span>        this.underlyingInputStream = Objects.requireNonNull(inputStream, "inputStream");<a name="line.152"></a>
<span class="sourceLineNo">153</span>        this.shutdownExecutorService = shutdownExecutorService;<a name="line.153"></a>
<span class="sourceLineNo">154</span>        this.activeBuffer = ByteBuffer.allocate(bufferSizeInBytes);<a name="line.154"></a>
<span class="sourceLineNo">155</span>        this.readAheadBuffer = ByteBuffer.allocate(bufferSizeInBytes);<a name="line.155"></a>
<span class="sourceLineNo">156</span>        this.activeBuffer.flip();<a name="line.156"></a>
<span class="sourceLineNo">157</span>        this.readAheadBuffer.flip();<a name="line.157"></a>
<span class="sourceLineNo">158</span>    }<a name="line.158"></a>
<span class="sourceLineNo">159</span><a name="line.159"></a>
<span class="sourceLineNo">160</span>    @Override<a name="line.160"></a>
<span class="sourceLineNo">161</span>    public int available() throws IOException {<a name="line.161"></a>
<span class="sourceLineNo">162</span>        stateChangeLock.lock();<a name="line.162"></a>
<span class="sourceLineNo">163</span>        // Make sure we have no integer overflow.<a name="line.163"></a>
<span class="sourceLineNo">164</span>        try {<a name="line.164"></a>
<span class="sourceLineNo">165</span>            return (int) Math.min(Integer.MAX_VALUE, (long) activeBuffer.remaining() + readAheadBuffer.remaining());<a name="line.165"></a>
<span class="sourceLineNo">166</span>        } finally {<a name="line.166"></a>
<span class="sourceLineNo">167</span>            stateChangeLock.unlock();<a name="line.167"></a>
<span class="sourceLineNo">168</span>        }<a name="line.168"></a>
<span class="sourceLineNo">169</span>    }<a name="line.169"></a>
<span class="sourceLineNo">170</span><a name="line.170"></a>
<span class="sourceLineNo">171</span>    private void checkReadException() throws IOException {<a name="line.171"></a>
<span class="sourceLineNo">172</span>        if (readAborted) {<a name="line.172"></a>
<span class="sourceLineNo">173</span>            if (readException instanceof IOException) {<a name="line.173"></a>
<span class="sourceLineNo">174</span>                throw (IOException) readException;<a name="line.174"></a>
<span class="sourceLineNo">175</span>            }<a name="line.175"></a>
<span class="sourceLineNo">176</span>            throw new IOException(readException);<a name="line.176"></a>
<span class="sourceLineNo">177</span>        }<a name="line.177"></a>
<span class="sourceLineNo">178</span>    }<a name="line.178"></a>
<span class="sourceLineNo">179</span><a name="line.179"></a>
<span class="sourceLineNo">180</span>    @Override<a name="line.180"></a>
<span class="sourceLineNo">181</span>    public void close() throws IOException {<a name="line.181"></a>
<span class="sourceLineNo">182</span>        boolean isSafeToCloseUnderlyingInputStream = false;<a name="line.182"></a>
<span class="sourceLineNo">183</span>        stateChangeLock.lock();<a name="line.183"></a>
<span class="sourceLineNo">184</span>        try {<a name="line.184"></a>
<span class="sourceLineNo">185</span>            if (isClosed) {<a name="line.185"></a>
<span class="sourceLineNo">186</span>                return;<a name="line.186"></a>
<span class="sourceLineNo">187</span>            }<a name="line.187"></a>
<span class="sourceLineNo">188</span>            isClosed = true;<a name="line.188"></a>
<span class="sourceLineNo">189</span>            if (!isReading) {<a name="line.189"></a>
<span class="sourceLineNo">190</span>                // Nobody is reading, so we can close the underlying input stream in this method.<a name="line.190"></a>
<span class="sourceLineNo">191</span>                isSafeToCloseUnderlyingInputStream = true;<a name="line.191"></a>
<span class="sourceLineNo">192</span>                // Flip this to make sure the read ahead task will not close the underlying input stream.<a name="line.192"></a>
<span class="sourceLineNo">193</span>                isUnderlyingInputStreamBeingClosed = true;<a name="line.193"></a>
<span class="sourceLineNo">194</span>            }<a name="line.194"></a>
<span class="sourceLineNo">195</span>        } finally {<a name="line.195"></a>
<span class="sourceLineNo">196</span>            stateChangeLock.unlock();<a name="line.196"></a>
<span class="sourceLineNo">197</span>        }<a name="line.197"></a>
<span class="sourceLineNo">198</span><a name="line.198"></a>
<span class="sourceLineNo">199</span>        if (shutdownExecutorService) {<a name="line.199"></a>
<span class="sourceLineNo">200</span>            try {<a name="line.200"></a>
<span class="sourceLineNo">201</span>                executorService.shutdownNow();<a name="line.201"></a>
<span class="sourceLineNo">202</span>                executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);<a name="line.202"></a>
<span class="sourceLineNo">203</span>            } catch (final InterruptedException e) {<a name="line.203"></a>
<span class="sourceLineNo">204</span>                final InterruptedIOException iio = new InterruptedIOException(e.getMessage());<a name="line.204"></a>
<span class="sourceLineNo">205</span>                iio.initCause(e);<a name="line.205"></a>
<span class="sourceLineNo">206</span>                throw iio;<a name="line.206"></a>
<span class="sourceLineNo">207</span>            } finally {<a name="line.207"></a>
<span class="sourceLineNo">208</span>                if (isSafeToCloseUnderlyingInputStream) {<a name="line.208"></a>
<span class="sourceLineNo">209</span>                    underlyingInputStream.close();<a name="line.209"></a>
<span class="sourceLineNo">210</span>                }<a name="line.210"></a>
<span class="sourceLineNo">211</span>            }<a name="line.211"></a>
<span class="sourceLineNo">212</span>        }<a name="line.212"></a>
<span class="sourceLineNo">213</span>    }<a name="line.213"></a>
<span class="sourceLineNo">214</span><a name="line.214"></a>
<span class="sourceLineNo">215</span>    private void closeUnderlyingInputStreamIfNecessary() {<a name="line.215"></a>
<span class="sourceLineNo">216</span>        boolean needToCloseUnderlyingInputStream = false;<a name="line.216"></a>
<span class="sourceLineNo">217</span>        stateChangeLock.lock();<a name="line.217"></a>
<span class="sourceLineNo">218</span>        try {<a name="line.218"></a>
<span class="sourceLineNo">219</span>            isReading = false;<a name="line.219"></a>
<span class="sourceLineNo">220</span>            if (isClosed &amp;&amp; !isUnderlyingInputStreamBeingClosed) {<a name="line.220"></a>
<span class="sourceLineNo">221</span>                // close method cannot close underlyingInputStream because we were reading.<a name="line.221"></a>
<span class="sourceLineNo">222</span>                needToCloseUnderlyingInputStream = true;<a name="line.222"></a>
<span class="sourceLineNo">223</span>            }<a name="line.223"></a>
<span class="sourceLineNo">224</span>        } finally {<a name="line.224"></a>
<span class="sourceLineNo">225</span>            stateChangeLock.unlock();<a name="line.225"></a>
<span class="sourceLineNo">226</span>        }<a name="line.226"></a>
<span class="sourceLineNo">227</span>        if (needToCloseUnderlyingInputStream) {<a name="line.227"></a>
<span class="sourceLineNo">228</span>            try {<a name="line.228"></a>
<span class="sourceLineNo">229</span>                underlyingInputStream.close();<a name="line.229"></a>
<span class="sourceLineNo">230</span>            } catch (final IOException e) {<a name="line.230"></a>
<span class="sourceLineNo">231</span>                // TODO ?<a name="line.231"></a>
<span class="sourceLineNo">232</span>            }<a name="line.232"></a>
<span class="sourceLineNo">233</span>        }<a name="line.233"></a>
<span class="sourceLineNo">234</span>    }<a name="line.234"></a>
<span class="sourceLineNo">235</span><a name="line.235"></a>
<span class="sourceLineNo">236</span>    private boolean isEndOfStream() {<a name="line.236"></a>
<span class="sourceLineNo">237</span>        return !activeBuffer.hasRemaining() &amp;&amp; !readAheadBuffer.hasRemaining() &amp;&amp; endOfStream;<a name="line.237"></a>
<span class="sourceLineNo">238</span>    }<a name="line.238"></a>
<span class="sourceLineNo">239</span><a name="line.239"></a>
<span class="sourceLineNo">240</span>    @Override<a name="line.240"></a>
<span class="sourceLineNo">241</span>    public int read() throws IOException {<a name="line.241"></a>
<span class="sourceLineNo">242</span>        if (activeBuffer.hasRemaining()) {<a name="line.242"></a>
<span class="sourceLineNo">243</span>            // short path - just get one byte.<a name="line.243"></a>
<span class="sourceLineNo">244</span>            return activeBuffer.get() &amp; 0xFF;<a name="line.244"></a>
<span class="sourceLineNo">245</span>        }<a name="line.245"></a>
<span class="sourceLineNo">246</span>        final byte[] oneByteArray = oneByte.get();<a name="line.246"></a>
<span class="sourceLineNo">247</span>        return read(oneByteArray, 0, 1) == EOF ? -1 : oneByteArray[0] &amp; 0xFF;<a name="line.247"></a>
<span class="sourceLineNo">248</span>    }<a name="line.248"></a>
<span class="sourceLineNo">249</span><a name="line.249"></a>
<span class="sourceLineNo">250</span>    @Override<a name="line.250"></a>
<span class="sourceLineNo">251</span>    public int read(final byte[] b, final int offset, int len) throws IOException {<a name="line.251"></a>
<span class="sourceLineNo">252</span>        if (offset &lt; 0 || len &lt; 0 || len &gt; b.length - offset) {<a name="line.252"></a>
<span class="sourceLineNo">253</span>            throw new IndexOutOfBoundsException();<a name="line.253"></a>
<span class="sourceLineNo">254</span>        }<a name="line.254"></a>
<span class="sourceLineNo">255</span>        if (len == 0) {<a name="line.255"></a>
<span class="sourceLineNo">256</span>            return 0;<a name="line.256"></a>
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<span class="sourceLineNo">258</span><a name="line.258"></a>
<span class="sourceLineNo">259</span>        if (!activeBuffer.hasRemaining()) {<a name="line.259"></a>
<span class="sourceLineNo">260</span>            // No remaining in active buffer - lock and switch to write ahead buffer.<a name="line.260"></a>
<span class="sourceLineNo">261</span>            stateChangeLock.lock();<a name="line.261"></a>
<span class="sourceLineNo">262</span>            try {<a name="line.262"></a>
<span class="sourceLineNo">263</span>                waitForAsyncReadComplete();<a name="line.263"></a>
<span class="sourceLineNo">264</span>                if (!readAheadBuffer.hasRemaining()) {<a name="line.264"></a>
<span class="sourceLineNo">265</span>                    // The first read.<a name="line.265"></a>
<span class="sourceLineNo">266</span>                    readAsync();<a name="line.266"></a>
<span class="sourceLineNo">267</span>                    waitForAsyncReadComplete();<a name="line.267"></a>
<span class="sourceLineNo">268</span>                    if (isEndOfStream()) {<a name="line.268"></a>
<span class="sourceLineNo">269</span>                        return EOF;<a name="line.269"></a>
<span class="sourceLineNo">270</span>                    }<a name="line.270"></a>
<span class="sourceLineNo">271</span>                }<a name="line.271"></a>
<span class="sourceLineNo">272</span>                // Swap the newly read read ahead buffer in place of empty active buffer.<a name="line.272"></a>
<span class="sourceLineNo">273</span>                swapBuffers();<a name="line.273"></a>
<span class="sourceLineNo">274</span>                // After swapping buffers, trigger another async read for read ahead buffer.<a name="line.274"></a>
<span class="sourceLineNo">275</span>                readAsync();<a name="line.275"></a>
<span class="sourceLineNo">276</span>            } finally {<a name="line.276"></a>
<span class="sourceLineNo">277</span>                stateChangeLock.unlock();<a name="line.277"></a>
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<span class="sourceLineNo">280</span>        len = Math.min(len, activeBuffer.remaining());<a name="line.280"></a>
<span class="sourceLineNo">281</span>        activeBuffer.get(b, offset, len);<a name="line.281"></a>
<span class="sourceLineNo">282</span><a name="line.282"></a>
<span class="sourceLineNo">283</span>        return len;<a name="line.283"></a>
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<span class="sourceLineNo">285</span><a name="line.285"></a>
<span class="sourceLineNo">286</span>    /** Read data from underlyingInputStream to readAheadBuffer asynchronously. */<a name="line.286"></a>
<span class="sourceLineNo">287</span>    private void readAsync() throws IOException {<a name="line.287"></a>
<span class="sourceLineNo">288</span>        stateChangeLock.lock();<a name="line.288"></a>
<span class="sourceLineNo">289</span>        final byte[] arr;<a name="line.289"></a>
<span class="sourceLineNo">290</span>        try {<a name="line.290"></a>
<span class="sourceLineNo">291</span>            arr = readAheadBuffer.array();<a name="line.291"></a>
<span class="sourceLineNo">292</span>            if (endOfStream || readInProgress) {<a name="line.292"></a>
<span class="sourceLineNo">293</span>                return;<a name="line.293"></a>
<span class="sourceLineNo">294</span>            }<a name="line.294"></a>
<span class="sourceLineNo">295</span>            checkReadException();<a name="line.295"></a>
<span class="sourceLineNo">296</span>            readAheadBuffer.position(0);<a name="line.296"></a>
<span class="sourceLineNo">297</span>            readAheadBuffer.flip();<a name="line.297"></a>
<span class="sourceLineNo">298</span>            readInProgress = true;<a name="line.298"></a>
<span class="sourceLineNo">299</span>        } finally {<a name="line.299"></a>
<span class="sourceLineNo">300</span>            stateChangeLock.unlock();<a name="line.300"></a>
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<span class="sourceLineNo">302</span>        executorService.execute(() -&gt; {<a name="line.302"></a>
<span class="sourceLineNo">303</span>            stateChangeLock.lock();<a name="line.303"></a>
<span class="sourceLineNo">304</span>            try {<a name="line.304"></a>
<span class="sourceLineNo">305</span>                if (isClosed) {<a name="line.305"></a>
<span class="sourceLineNo">306</span>                    readInProgress = false;<a name="line.306"></a>
<span class="sourceLineNo">307</span>                    return;<a name="line.307"></a>
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<span class="sourceLineNo">309</span>                // Flip this so that the close method will not close the underlying input stream when we<a name="line.309"></a>
<span class="sourceLineNo">310</span>                // are reading.<a name="line.310"></a>
<span class="sourceLineNo">311</span>                isReading = true;<a name="line.311"></a>
<span class="sourceLineNo">312</span>            } finally {<a name="line.312"></a>
<span class="sourceLineNo">313</span>                stateChangeLock.unlock();<a name="line.313"></a>
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<span class="sourceLineNo">316</span>            // Please note that it is safe to release the lock and read into the read ahead buffer<a name="line.316"></a>
<span class="sourceLineNo">317</span>            // because either of following two conditions will hold:<a name="line.317"></a>
<span class="sourceLineNo">318</span>            //<a name="line.318"></a>
<span class="sourceLineNo">319</span>            // 1. The active buffer has data available to read so the reader will not read from the read ahead buffer.<a name="line.319"></a>
<span class="sourceLineNo">320</span>            //<a name="line.320"></a>
<span class="sourceLineNo">321</span>            // 2. This is the first time read is called or the active buffer is exhausted, in that case the reader waits<a name="line.321"></a>
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<span class="sourceLineNo">323</span>            //<a name="line.323"></a>
<span class="sourceLineNo">324</span>            // So there is no race condition in both the situations.<a name="line.324"></a>
<span class="sourceLineNo">325</span>            int read = 0;<a name="line.325"></a>
<span class="sourceLineNo">326</span>            int off = 0, len = arr.length;<a name="line.326"></a>
<span class="sourceLineNo">327</span>            Throwable exception = null;<a name="line.327"></a>
<span class="sourceLineNo">328</span>            try {<a name="line.328"></a>
<span class="sourceLineNo">329</span>                // try to fill the read ahead buffer.<a name="line.329"></a>
<span class="sourceLineNo">330</span>                // if a reader is waiting, possibly return early.<a name="line.330"></a>
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<span class="sourceLineNo">332</span>                    read = underlyingInputStream.read(arr, off, len);<a name="line.332"></a>
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<span class="sourceLineNo">336</span>                    off += read;<a name="line.336"></a>
<span class="sourceLineNo">337</span>                    len -= read;<a name="line.337"></a>
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<span class="sourceLineNo">339</span>            } catch (final Throwable ex) {<a name="line.339"></a>
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<span class="sourceLineNo">343</span>                    // The user can see Error in UncaughtExceptionHandler.<a name="line.343"></a>
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<span class="sourceLineNo">346</span>            } finally {<a name="line.346"></a>
<span class="sourceLineNo">347</span>                stateChangeLock.lock();<a name="line.347"></a>
<span class="sourceLineNo">348</span>                try {<a name="line.348"></a>
<span class="sourceLineNo">349</span>                    readAheadBuffer.limit(off);<a name="line.349"></a>
<span class="sourceLineNo">350</span>                    if (read &lt; 0 || (exception instanceof EOFException)) {<a name="line.350"></a>
<span class="sourceLineNo">351</span>                        endOfStream = true;<a name="line.351"></a>
<span class="sourceLineNo">352</span>                    } else if (exception != null) {<a name="line.352"></a>
<span class="sourceLineNo">353</span>                        readAborted = true;<a name="line.353"></a>
<span class="sourceLineNo">354</span>                        readException = exception;<a name="line.354"></a>
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<span class="sourceLineNo">356</span>                    readInProgress = false;<a name="line.356"></a>
<span class="sourceLineNo">357</span>                    signalAsyncReadComplete();<a name="line.357"></a>
<span class="sourceLineNo">358</span>                } finally {<a name="line.358"></a>
<span class="sourceLineNo">359</span>                    stateChangeLock.unlock();<a name="line.359"></a>
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<span class="sourceLineNo">361</span>                closeUnderlyingInputStreamIfNecessary();<a name="line.361"></a>
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<span class="sourceLineNo">363</span>        });<a name="line.363"></a>
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<span class="sourceLineNo">365</span><a name="line.365"></a>
<span class="sourceLineNo">366</span>    private void signalAsyncReadComplete() {<a name="line.366"></a>
<span class="sourceLineNo">367</span>        stateChangeLock.lock();<a name="line.367"></a>
<span class="sourceLineNo">368</span>        try {<a name="line.368"></a>
<span class="sourceLineNo">369</span>            asyncReadComplete.signalAll();<a name="line.369"></a>
<span class="sourceLineNo">370</span>        } finally {<a name="line.370"></a>
<span class="sourceLineNo">371</span>            stateChangeLock.unlock();<a name="line.371"></a>
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<span class="sourceLineNo">374</span><a name="line.374"></a>
<span class="sourceLineNo">375</span>    @Override<a name="line.375"></a>
<span class="sourceLineNo">376</span>    public long skip(final long n) throws IOException {<a name="line.376"></a>
<span class="sourceLineNo">377</span>        if (n &lt;= 0L) {<a name="line.377"></a>
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<span class="sourceLineNo">380</span>        if (n &lt;= activeBuffer.remaining()) {<a name="line.380"></a>
<span class="sourceLineNo">381</span>            // Only skipping from active buffer is sufficient<a name="line.381"></a>
<span class="sourceLineNo">382</span>            activeBuffer.position((int) n + activeBuffer.position());<a name="line.382"></a>
<span class="sourceLineNo">383</span>            return n;<a name="line.383"></a>
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<span class="sourceLineNo">385</span>        stateChangeLock.lock();<a name="line.385"></a>
<span class="sourceLineNo">386</span>        long skipped;<a name="line.386"></a>
<span class="sourceLineNo">387</span>        try {<a name="line.387"></a>
<span class="sourceLineNo">388</span>            skipped = skipInternal(n);<a name="line.388"></a>
<span class="sourceLineNo">389</span>        } finally {<a name="line.389"></a>
<span class="sourceLineNo">390</span>            stateChangeLock.unlock();<a name="line.390"></a>
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<span class="sourceLineNo">392</span>        return skipped;<a name="line.392"></a>
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<span class="sourceLineNo">395</span>    /**<a name="line.395"></a>
<span class="sourceLineNo">396</span>     * Internal skip function which should be called only from skip(). The assumption is that the stateChangeLock is<a name="line.396"></a>
<span class="sourceLineNo">397</span>     * already acquired in the caller before calling this function.<a name="line.397"></a>
<span class="sourceLineNo">398</span>     *<a name="line.398"></a>
<span class="sourceLineNo">399</span>     * @param n the number of bytes to be skipped.<a name="line.399"></a>
<span class="sourceLineNo">400</span>     * @return the actual number of bytes skipped.<a name="line.400"></a>
<span class="sourceLineNo">401</span>     */<a name="line.401"></a>
<span class="sourceLineNo">402</span>    private long skipInternal(final long n) throws IOException {<a name="line.402"></a>
<span class="sourceLineNo">403</span>        assert stateChangeLock.isLocked();<a name="line.403"></a>
<span class="sourceLineNo">404</span>        waitForAsyncReadComplete();<a name="line.404"></a>
<span class="sourceLineNo">405</span>        if (isEndOfStream()) {<a name="line.405"></a>
<span class="sourceLineNo">406</span>            return 0;<a name="line.406"></a>
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<span class="sourceLineNo">408</span>        if (available() &gt;= n) {<a name="line.408"></a>
<span class="sourceLineNo">409</span>            // we can skip from the internal buffers<a name="line.409"></a>
<span class="sourceLineNo">410</span>            int toSkip = (int) n;<a name="line.410"></a>
<span class="sourceLineNo">411</span>            // We need to skip from both active buffer and read ahead buffer<a name="line.411"></a>
<span class="sourceLineNo">412</span>            toSkip -= activeBuffer.remaining();<a name="line.412"></a>
<span class="sourceLineNo">413</span>            assert toSkip &gt; 0; // skipping from activeBuffer already handled.<a name="line.413"></a>
<span class="sourceLineNo">414</span>            activeBuffer.position(0);<a name="line.414"></a>
<span class="sourceLineNo">415</span>            activeBuffer.flip();<a name="line.415"></a>
<span class="sourceLineNo">416</span>            readAheadBuffer.position(toSkip + readAheadBuffer.position());<a name="line.416"></a>
<span class="sourceLineNo">417</span>            swapBuffers();<a name="line.417"></a>
<span class="sourceLineNo">418</span>            // Trigger async read to emptied read ahead buffer.<a name="line.418"></a>
<span class="sourceLineNo">419</span>            readAsync();<a name="line.419"></a>
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<span class="sourceLineNo">422</span>        final int skippedBytes = available();<a name="line.422"></a>
<span class="sourceLineNo">423</span>        final long toSkip = n - skippedBytes;<a name="line.423"></a>
<span class="sourceLineNo">424</span>        activeBuffer.position(0);<a name="line.424"></a>
<span class="sourceLineNo">425</span>        activeBuffer.flip();<a name="line.425"></a>
<span class="sourceLineNo">426</span>        readAheadBuffer.position(0);<a name="line.426"></a>
<span class="sourceLineNo">427</span>        readAheadBuffer.flip();<a name="line.427"></a>
<span class="sourceLineNo">428</span>        final long skippedFromInputStream = underlyingInputStream.skip(toSkip);<a name="line.428"></a>
<span class="sourceLineNo">429</span>        readAsync();<a name="line.429"></a>
<span class="sourceLineNo">430</span>        return skippedBytes + skippedFromInputStream;<a name="line.430"></a>
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<span class="sourceLineNo">432</span><a name="line.432"></a>
<span class="sourceLineNo">433</span>    /**<a name="line.433"></a>
<span class="sourceLineNo">434</span>     * Flips the active and read ahead buffer<a name="line.434"></a>
<span class="sourceLineNo">435</span>     */<a name="line.435"></a>
<span class="sourceLineNo">436</span>    private void swapBuffers() {<a name="line.436"></a>
<span class="sourceLineNo">437</span>        final ByteBuffer temp = activeBuffer;<a name="line.437"></a>
<span class="sourceLineNo">438</span>        activeBuffer = readAheadBuffer;<a name="line.438"></a>
<span class="sourceLineNo">439</span>        readAheadBuffer = temp;<a name="line.439"></a>
<span class="sourceLineNo">440</span>    }<a name="line.440"></a>
<span class="sourceLineNo">441</span><a name="line.441"></a>
<span class="sourceLineNo">442</span>    private void waitForAsyncReadComplete() throws IOException {<a name="line.442"></a>
<span class="sourceLineNo">443</span>        stateChangeLock.lock();<a name="line.443"></a>
<span class="sourceLineNo">444</span>        try {<a name="line.444"></a>
<span class="sourceLineNo">445</span>            isWaiting.set(true);<a name="line.445"></a>
<span class="sourceLineNo">446</span>            // There is only one reader, and one writer, so the writer should signal only once,<a name="line.446"></a>
<span class="sourceLineNo">447</span>            // but a while loop checking the wake up condition is still needed to avoid spurious wakeups.<a name="line.447"></a>
<span class="sourceLineNo">448</span>            while (readInProgress) {<a name="line.448"></a>
<span class="sourceLineNo">449</span>                asyncReadComplete.await();<a name="line.449"></a>
<span class="sourceLineNo">450</span>            }<a name="line.450"></a>
<span class="sourceLineNo">451</span>        } catch (final InterruptedException e) {<a name="line.451"></a>
<span class="sourceLineNo">452</span>            final InterruptedIOException iio = new InterruptedIOException(e.getMessage());<a name="line.452"></a>
<span class="sourceLineNo">453</span>            iio.initCause(e);<a name="line.453"></a>
<span class="sourceLineNo">454</span>            throw iio;<a name="line.454"></a>
<span class="sourceLineNo">455</span>        } finally {<a name="line.455"></a>
<span class="sourceLineNo">456</span>            isWaiting.set(false);<a name="line.456"></a>
<span class="sourceLineNo">457</span>            stateChangeLock.unlock();<a name="line.457"></a>
<span class="sourceLineNo">458</span>        }<a name="line.458"></a>
<span class="sourceLineNo">459</span>        checkReadException();<a name="line.459"></a>
<span class="sourceLineNo">460</span>    }<a name="line.460"></a>
<span class="sourceLineNo">461</span>}<a name="line.461"></a>




























































</pre>
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